Fallacies 2 (Powerpoint)

Fallacies 2
IS THE EVIDENCE RELIABLE?
Appeal to Probability
Just because something is possible does not
mean it is true.
Sample Student Homework
“‘Ancient Aliens’ is misleading because on the
show they claim that alien technology was
needed to move the stones for the pyramids.
But people could have moved the stones in
some other way.”
Appeal to Probability
1. The show says there was only one way to
move the stones: aliens.
2. Maybe there were other ways to do it.
3. Therefore, there were other ways to do it.
4. Therefore, the show is misleading: there is
not only one way to move the stones.
Give Me Another Explanation!
You cannot prove that the
show is misleading by
saying maybe it is saying
something false.
You have to show that it is
saying something false.
Argument from Ignorance
“Absence of evidence is not evidence of
absence.” – Carl Sagan
Just because there is no evidence that
something is true, does not mean that it is false.
Just because there is no evidence that
something is false, does not mean that it is true.
Argument from Ignorance
The argument from ignorance goes like this:
“You can’t prove that God doesn’t exist.
Therefore God exists.”
It assumes that because there is no argument
against a position, that that position must be
correct.
Shifting the Burden of Proof
A similar fallacy is “shifting the burden of proof”.
It goes:
“God exists. If you think otherwise, prove that
he doesn’t!”
Here, you make a claim (“God exists”) but
instead of giving evidence for it, you require that
your opponent give evidence for the opposite.
Harry Potter
• Best selling book series
in history.
• Highest grossing film
series in history.
• “Harry Potter and the
Prisoner of Azkaban”
won the Hugo Award
for best Novel.
“Just Asking Questions”
Frequently, conspiracy theorists will use a subtle
form of the argument from ignorance:
Is X true? I don’t know. I’m just asking questions.
[No arguments are presented for thinking X is
not true]
[Audience invited to conclude that X is true.]
“Just Asking Questions”
Some people think that George W. Bush was
responsible for the 9/11 terrorist attack in the
US. Was he responsible? Was the US
Government trying to invent a reason to attack
Israel’s enemies? I don’t know. I’m just asking
questions.
Argument from Incredulity
Similar to the argument from ignorance is the
argument from incredulity.
This happens on “Ancient Aliens” all the time:
• I can’t believe that X is true.
• Therefore, X is false.
Cousins?
Ad Hominem
You cannot show that someone’s claim is false
by showing that they are a bad person or that
they are not an expert.
You can show that we have no reason to believe
them. But to show that their claims are false we
need to have evidence that their claims are
false.
Erich von Däniken
• Author of Chariots of
the Gods in 1968.
• One of the first to argue
for ancient astronauts/
ancient aliens.
• Inspired many of the
people on the show.
Erich von Däniken
• Left school at 19.
• Does not have a college
degree.
• Does not have a PhD.
• Has never received
honors, recognition, or
rewards from experts.
• Has been convicted of
fraud twice.
Appeal to Motive
A version of the ad hominem fallacy is the
appeal to motive. You cannot show that a claim
is false by showing that the person making the
claim has a strong reason to believe it or a
strong reason to make you believe it.
Sample Homework
“‘Ancient Aliens’ is
misleading because in the
show, they present Erich
von Däniken arguing for
the claim that aliens
visited the Earth long ago.
But von Däniken wants
you to believe that so you
will buy his books and
make him rich.”
Another Example: AGW Conspiracy
Global warming “is a
multibillion-dollar
worldwide industry,
created by fanatically antiindustrial
environmentalists,
supported by scientists
peddling scare stories to
chase funding, and
propped up by compliant
politicians and the media.”
Distribution Fallacy
The distribution fallacy is committed when we
assume that individuals have the properties of
groups they belong to.
Lingnan has an excellent philosophy
department.
I am a philosopher at Lingnan._________
Therefore, I am an excellent philosopher.
Distribution Fallacy
Kooks and quacks will often try to make their
theories sound better “by association”:
• Having a PhD.
• Making one’s work sound “science-y”.
• Debating serious scholars.
• Associating oneself with respectable
institutions (Stanford, Smithsonian, etc.)
1. For the “whole” of Hong Kong kindergartens,
there is enough space for all children to go to
school.
2. Demand is for 168,000 spaces, but there are
a total of 241,000 spaces.
3. Therefore, there is no shortage of space in
kindergartens.
Distribution Fallacy
Just because there is enough space in the whole
system does not mean there is enough space in
the high-demand districts.
Mainlanders want to go to kindergarten in the
northern districts, because that’s closer to
China. These kindergarten seats have much
lower availability.
Genetic Fallacy
The genetic fallacy seeks to evaluate a claim on
the basis of its origin.
So, for example, someone might say, “Eugenics
is wrong, because the Nazis began it and did
horrible things for its sake.”
Eugenics may be wrong, but the fact that the
Nazis began it is irrelevant to this claim.
False Balance
False Balance
Often newspapers will present two sides of an
issue equally to provide “balance.”
Objectivity is good and biased reporting is bad.
But it is the responsibility of the news media to
present things in a way that accurately reflects
what we know to be true.
False Balance
False balance happens when:
• An issue is presented as having two sides
when no knowledgeable experts disagree.
• Two sides to an issue are presented equally
when one side has much more evidence than
the other.
• One side is allowed to present fallacious
arguments designed to mislead without the
reporter(s) indicating this.
“Teach the Controversy”
“Teach the Controversy”
Fallacy of the Mean
Candidate 1: “We should raise taxes on
everyone”
Candidate 2: “We should cut social programs”
Therefore,
Compromise: We should raise taxes on everyone
a little and cut social programs a little.
The Fallacy of the Mean
“Lol, debunked. Not exactly. There are always
two sides to a coin and the truth usually lies in
the middle. Of course not everything on Ancient
Aliens is totally true. Of course, not everything
on this video is unbiased either.”
– internet commenter Darkeus regarding Chris
White’s film “Ancient Aliens Debunked”
Tu Quoque
“Tu quoque” is Latin for “you too”. It’s a defense
of an invalid argument that goes:
“You’ve made a similar argument. So you cannot
criticize the flaws in this argument.”
Just because other people are doing it doesn’t
make it right!
DOES THE EVIDENCE SUPPORT THE
CONCLUSION?
Appeal to Popularity
“Millions of people around the world believe
that we have been visited in the past by
extraterrestrial beings.” – Narrator from
“Ancient Aliens”
Appeal to Popularity
“What I am saying is that there is doubt. Millions
of people believe in God in the US, so to teach
to kids (again under the age of 18) only one side
of something that ‘could be’ something else is
misleading.” – comment from the internet
Appeal to Popularity
“Indian astrology is famous in the entire world.
From ancient time astrology has been improving
in this country. Millions of people believe in
astrology with which the way of life can be
smooth. Proper guidance can make a person
able to combat against the problematic
situations and unexpected happenings. A good
astrologer can really give this guidance.” –
article about astrologers in Delhi
Appeal to Tradition
“[India] is also home to
some of the oldest records
of ancient technologies.
Ancient Sanskrit texts,
dating back as far as 6,000
BC describe in varied, but
vivid detail, flying
machines called
‘vimanas’” – Narrator
from “Ancient Aliens”
Appeal to Tradition
“With a history of more
than 2000 years,
Traditional Chinese
Medicine (TCM) has
formed a unique system
to diagnose and cure
illness.” – eastday.com
Not Fallacies
The following things are not fallacies:
• Having traditions
• Being popular
• Lacking evidence
Appeal to Tradition
Some people have the “traditional” belief that
keeping a pet turtle slows down your business
and ruins your fortune.
There are lots of reasons they might have for
this: belief in sympathetic magic, confirmation
bias, hearsay, etc. None of these are good
reasons.
Appeal to Tradition
But just because someone has a traditional
belief that is false and held for bad reasons does
not mean they’ve committed the ‘appeal to
tradition’ fallacy.
The fallacy only happens when someone
presents the fact that this is a traditional belief
as a reason to believe it.
Appeal to Tradition
“Marriage has traditionally been between a man
and a woman, therefore, gay marriage should
not be allowed.”
Appeal to Popularity
Many things are popular and widely believed.
Some of them are false – like the belief that
aliens visited ancient humans on Earth.
This does not mean that the ‘appeal to
popularity’ fallacy has been committed!
Bad Reasons
Bad reasons to believe in aliens:
• Erich von Daniken told you to.
• That gold thingy sort of looks like a spaceship.
• Ancient Indian texts talk about flying chariots
called ‘vimanas.’
• No one could build the pyramids without the
help of alien technology.
• It’s possible for aliens to come and visit.
Appeal to Popularity
If those are the reasons you believe aliens came
to Earth, then you are not committing the
appeal to popularity fallacy – even if your belief
is a popular one!
To commit the fallacy, you have to argue that
the reason to believe in aliens is that lots of
other people believe in aliens.
Appeal to Popularity
“In history, Buddhists talk about karma.
Christians talk about deeds. Taoists talk about
te. Other spiritual beings talk about virtue.
These are different words for the same thing.
Millions of people believe in karma. Millions of
people desperately want to clear their own
karma.” -- The Power of Soul, Zhi Gang Sha
(Also note equivocation)
Red Herring
Red Herring
What Does It Have To Do with Aliens?
• The wings are not shaped like normal bird
wings.
• The tail is vertical rather than horizontal.
That’s not how bird tails look.
• The wings curve down as they move outward
from the bird. This would help something fly.
• The wings are thicker in the middle and
thinner at the edges. This would help
something fly.
Appeal to Nature: Meat Eating
“Your statement that "we were born to eat meat" is
nonsense. In using comparative anatomy to
determine what man was "meant" to eat, we
should look at the species most similar to man,
namely the anthropoid apes — chimpanzees,
gibbons, gorillas, and orangutans. Of all animals,
man's digestive organs and teeth most closely
resemble these apes. In captivity, some of these
animals will eat meat if forced to rather than starve
to death. But in the wild, all eat a vegetarian diet.”
Eating a Slow Loris
Appeal to Nature: Medicine
Taiwan has the highest per-capita incidence of
UUC (upper urinary tract cancer) of anywhere in
the world.
Plants of the genera Ephedra and Asarum
produce the toxic chemical aristolochic acid
which causes UUC.
TCM herbal remedies contain lots of these
plants, and tests have shown they contain
aristolochic acid as well.
Appeal to Nature: Homosexuality
“Because of this, God gave them over to
shameful lusts. Even their women exchanged
natural sexual relations for unnatural ones. In
the same way the men also abandoned natural
relations with women and were inflamed with
lust for one another.” Romans 1:26-27
“Born This Way”
Don't hide yourself in
regret,
Just love yourself and
you're set
I'm on the right track,
baby
I was born this way
Ooh, there ain't no other
way, baby, I was born this
way
Baby, I was born this way
Homosexuality in Nature
Homosexual behavior has
been observed in as many
as 1,500 animal species.
For example, about 1/3 of
albatross couples (pairs
that bond for life) are
made up of two female
albatrosses.
Appeal to Nature: Evolution
According to the theory of evolution, the strong
survive and the weak die.
Greed and aggression are traits that humans
have because they have helped us in the past to
succeed against people who share and are nice.
So, according to the theory of evolution, greed
and aggression are natural and good.
But they are not good! So evolution is false.
False Equivocation
Equivocation (or “false equivocation”) is when
one word is used with two meanings in the
same argument, rendering it invalid.
Silly Example
God is love.
Love is blind.
Ray Charles is blind.
So, Ray Charles is God.
False Equivocation
If evolution is true, then we should expect that
creatures act selfishly.
If evolution is true, then creatures ought to act
selfishly.
But we know that it’s morally wrong to act
selfishly.
Creatures ought not to act selfishly.
So evolution is false.
Post Hoc Ergo Propter Hoc
https://www.youtube.com/watch?v=_0_suZntks
THE MOST IMPORTANT LOGICAL
FALLACY
The Fallacy Fallacy
This is a bad argument:
1. You have presented argument A for your
claim C.
2. A is a fallacious argument.
3. Therefore, C is false.
Critical Thinking
Is there any evidence to support the claim?
Is the evidence reliable and trustworthy? How
reliable is it? Should you accept it?
Does the evidence actually support the claim?
Is there other evidence you should consider?
What CT Can Do
• Critical thinking can show that there is no
evidence.
• Critical thinking can show that the evidence is
unreliable or untrustworthy.
• Critical thinking can show that the evidence
does not support the claim in question.
• Critical thinking can (sometimes) reveal the
other evidence you should consider.
What CT Cannot Do
Critical thinking cannot (by itself) show that a
claim is false.
It checks arguments and makes sure they are
not fallacious.
Only hard work and real-world investigation can
show that claims are true or false.
What I Did
• Demonstrated that some arguments for
Ancient Alien Theory are fallacious.
• Demonstrated that some arguments against
global warming are fallacious.
• Demonstrated that some arguments against
the theory of evolution are fallacious.
• Demonstrated that some arguments for/
against homosexuality are fallacious.
What I Have Not Done
• Show that Ancient Aliens Theory is false.
• Show that Anthropogenic Global Warming is
true.
• Show that the Theory of Evolution is true.
• Show that homosexuality is good/ is bad.
ECOLOGICAL FALLACY
Ecological Fallacy
Here’s an “ecological inference”.
Countries where, on average, people consume
more fat have higher rates of breast cancer.
Therefore, consuming more fat leads to a higher
risk of breast cancer.
There’s a potential problem here with
“confounding variables”.
Maybe countries that consume more fat, on
average, are also countries that have more
pollution, on average (perhaps because
pollution and fat consumption both correlate
with poverty). So maybe it’s the pollution and
not the fat that causes breast cancer.
Ecological Fallacy
But let’s assume we know there aren’t any
confounding variables. Does the premise
support the conclusion:
Premise: Countries that on average consume
more fat on average have higher rates of breast
cancer.
Conclusion: Consuming fat leads to a higher risk
for breast cancer.
Ecological Fallacy
But the conclusion doesn’t follow.
Suppose that in Country A (10 people):
5 people eat 4 pounds of fat a day.
5 people eat 0 pounds of fat a day.
Average fat consumption: 2 pounds/ day.
Ecological Fallacy
In Country B (also 10 people):
5 people eat 2 pounds of fat/ day
5 people eat 1 pound of fat/ day
Average fat consumption 1.5 pounds fat/ day.
Country B on average consumes less fat.
Ecological Fallacy
Now assume that in Country A, all 5 people who
consume no fat get breast cancer. And in
Country B, no one gets breast cancer.
So on average, Country B consumes less fat and
has a lower rate of breast cancer. Country B
consumes more fat and has a higher rate of
breast cancer.
Ecological Fallacy
But still, this doesn’t mean people who consume
more fat are more likely to get breast cancer.
It’s the people who consume no fat that get
cancer!
Ecological Fallacy
A famous (purported) instance of the ecological
fallacy was Durkheim’s argument that since
suicide rates in Catholic countries were lower
than in Protestant countries, Catholics were less
likely to commit suicide than Protestants.